Cryptocurrencies and money can all have value if agreed upon.  The nature of other assets such as stocks, gold, silver, debt securities and others will also be valuable if one party and the other party have an agreement that it is valuable.  Can bitcoins be abandoned?  It's very possible if there are no more miners and people using it.  Likewise with money if the state/party that issued it is no longer trusted by the public.  It's a very simple world.